1. Field of the Invention
The present invention relates to managing the information of a player character (PC) to be transmitted to each client system (or communication terminal) in a network game, with flags.
2. Description of the Related Art
In a network game in which client systems (or communication terminals) used by an indefinite number of players are connected with a game server, each client system (or communication terminal) has to display a player character (PC) controlled by a player of the client system and player characters (PCs) controlled by other players.
When the information on the player character (PC) is to be transmitted from the game server to each client (or communication terminal), the information on the player characters (PC) increases according to the number of player characters (PC) to be displayed. This increased number of player characters to be displayed degrades the network response to the game server.
In the network game in which the positions of the individual player characters (PCs) are managed by the game server, there has been conceived a method in which: an area where each player character (PC) can move is divided into virtual cells; the information of each player character (PC) is selected at the unit of each cell; one player character (PC) similar to another is selected; and the information on that player character (PC) is transmitted.
As shown in FIG. 10, specifically, the area where each player character (PC) can move is assumed to be an arbitrary field F, which is divided into two-dimensional cells (0, 0) to (3, 2). It is then assumed that a character A selected by a player is located at (1, 1) whereas characters B and C selected by other players are located at (2, 2). The data structure of this case is:                Cell (1, 1)→A→NULL;and        Cell (2, 2)→B→C→NULL.        
In case where anew character is added, as shown in FIG. 11, a cell is calculated based upon the coordinates where the new character (at step 1101) exists, and is registered in a cell linked list of the calculated cell (at step 1102) Here, the cell linked list means a management table for linking a cell and a character existing in the cell. When the character is modified (or moved), as shown in FIG. 12, the cell is calculated based upon the coordinates before the movement of the character (at step 1201), and is deleted from the cell linked list of the cells before the movement (at Step 1202). Then, the cell where the moved character exists is calculated based upon the coordinates after the movement (at Step 1203). Then, the character is registered (at Step 1204) in the cell linked list of the cells after the movement.
In case a character is deleted (or erased), as shown in FIG. 13, the cell before movement is calculated based upon the coordinates before the movement of the character (at Step 1301), and the cells before the movement are deleted from the cell linked list (at Step 1302). In the case of detecting characters within a predetermined distance between the characters, as shown in FIG. 14: cells within the range of a predetermined distance are calculated (at Step 1401) and are identified (at Step 1402); player characters (PC) existing in the identified cells are enumerated (at Step 1403). It is then decided (at Step 1404) whether each player character (PC) is within the predetermined distance. Predetermined processing is done (at Step 1405) if identified player characters are within the predetermined distance. After the processing, the logic transfers to the cell identification (at Step 1402). If the player characters are not within the predetermined distance, the logic returns to the cell enumeration (at step 1402). Here, the predetermined distance between the characters is the area enclosed by a circle around the character A as shown in FIG. 10. Moreover, this circled area corresponds to the display area of the screen of the client (or communication terminal) controlling the character A.
Moreover, the predetermined processing at (Step 1405) is processing during the network game and processing covering all the following processing by using a near member list or a list of the characters within a predetermined range:    1) To transmit a chat message;    2) To search for the enemies of the player characters or non-player characters (NPC); and    3) To transmit the positions of the player characters to the clients (or communication terminals).
In the aforementioned method of the prior art for transmitting the information on another player character (PC) near one player character (PC), the information of the player character (PC) to be displayed has to be fully transmitted at each time. In case where a number of characters are to be simultaneously moved or change their equipment, therefore, the quantity of information increases to cause a problem that the network response to the game server deteriorates.